Ecological Effects of Fire - School of Forest Resources & Conservation

Report
Ecological Effects- short version
Chapter IX: Interagency Prescribed Fire Training
Leda N. Kobziar
School of Forest Resources and Conservation
University of Florida

Objective: Understand the what
and how of fire’s role in Florida’s
ecosystems

Fire dependent ecosystems of
Florida, their fire regimes

Fire’s effects on ecosystem
components e.g. water, soil,
vegetation, fauna

Relationship between
timing/season of fire and ecosystem
effects

How to manipulate fire regime
attributes to encourage specific
ecological responses
Objectives
1) Identify fire’s primary effects on the basic physical ecosystem
components of water and soils.
2) Identify fire’s primary effects on floral (plants) and faunal
(animal) components of ecosystems.
3) Identify common Florida fire-dependent ecosystems and
frequency of fire return intervals that sustain them (IN YOUR
BOOK)
4) Understand the relationship between season or timing of fire
applications and certain ecosystem responses.
5) Understand the connection between burn prescription
parameters and ecological effects.
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Fire history (pyrodendrochronology,
reconstructions, sediment and pollen
charcoal analyses)
Fire regimes
Fire dependence or adaptations of
plants and animals- AUTECOLOGY
Fire effects on water, plants, animals,
from individuals to populations,
communities, ecosystems,
landscapes.
Fire effects on nutrient, energy, and
carbon cycling
# of Lightning Fire Acres
1986-1997
# of Acres (x 1000)
300
300
250
250
200
200
150
150
100
100
50
50
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
# Acres
Florida’s Historical Fire Regime: May-June
 Native Americans burned to stimulate grasses and forage, acorn production,
reduce fuels and pests, clear land for agroforestry, increase access, herd game,
etc.
 Practices adopted by European Settlers (c. 1700s to mid 1900s)

Thousands of yrs of repeated
burning ecosystem structure &
composition
 Selected for fire-resistant or firedependent species (e.g. longleaf
pine, red cockaded woodpecker)
and communities
 Resulted in 26 fire dependent
and/or influenced communities
in Florida alone (1/3rd of 81
total).
Chris Evans


The Florida Natural Areas Inventory lists 81 communities in Florida:
18 of these are considered FIRE DEPENDENT– will change
significantly if any aspect of the fire regime is changed for a given
length of time.
These ecosystems cover the majority of non-developed land area
in Florida. Examples:
 Sandhill, Upland Pine
 Scrub
 Dry Prairie
 Mesic Flatwoods
 Scrubby Flatwoods
 Wet Flatwoods
 Glades Marsh
 Marl Prairie
Frequent, 1-3 yrs
Variable, 5-30 yrs
Frequent, 1-2 yrs
Frequent, 1-4 yrs
Variable, 5-15 yrs
Frequent, 3-10 yrs
approx. 2-5 yrs
Frequent, 1-6 yrs
UNSUSTAINABLE HARVESTING & FIRE
SUPPRESSION  FOREST DEGRADATION: ~3%
ORIGINAL FOREST REMAINING
1) Lack of seed sources,
regeneration of fire
adapted species
2) Altered soil fertility, pH,
texture, mycorrhizae…
3) Loss of fire-structure
dependent wildlife spp.
4) Closed communities with
limited early
successional species
recruitment
5) Changes in flammability
and fuels structure
6) Fuel load build-up 
larger, less predicable,
higher severity, more
costly wildfires
IN THE SOUTH, REVERSING THE LEGACY OF SUPPRESSION
AND DEGRADATION MEANS USING PRESCRIBED FIRE TO
RESTORE AND MAINTAIN NATIVE ECOSYSTEMS
FIRE REGIME ATTRIBUTES
• Fire frequency
• Seasonality
• Extent of area burned/
landscape heterogeneity
•
•
•
•
Type (crown, ground, surface)
Intensity
Severity
Synergy, interaction with other disturbances
• Includes using fire with mechanical
treatments, silviculture, CLIMATE
Frequent
fire
Infrequent
fire
Randy Cyr
Longleaf pine
Southeastern US
Fire 1-4 years
Low intensity, understory,
Spring/ summer
Florida Big Scrub (sand
pine) Fire 30+ years,
high intensity, crown,
spring or summer, large
areas
Basin swamp
Fire > 5-150 years, small
area, mixed severity, only
burns during drought (peaty
soils)
The South burns more than any other region of similar size
in the world…but still doesn’t meet fire rotation goals


Southern Region:
354 M acres forest pre-settlement
 How many acres would have burned historically to
maintain a 10-yr average FRI across the forests?
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

200 M acres forest today
8 M burned…how much more should be
burned?
Caveat: “forest” includes plantations, which are not subject
to the historical FRI…but you get the picture!
F I R E R E G I M E S C O R R E S P O N D T O T H E D I S T R I B U T I O N O F F L N AT I V E E C O S Y S T E M S
Marsh
Shrub Wetland
Bay head
Hydric
Hammock
Pine
Flatwoods
Slash
pine
scrub
Sand Pine
Scrub
Savanna
Depth to Water Table (m)
Low scrub
High
Pine
Mesic
Hammock
Rosemary
Rosemary
scrub
scrub
Oak
scrub
Rosemary
Bald
Fire Interval
Xeric
Hammock
Without fire sand
pine scrub will
likely succeed to
xeric oak/hickory
scrub.
Fire Regime
• 30+ year fire return interval
• Late spring / early summer fires
associated w/ drought, high winds,
low RH and high temperature
• High-intensity, larges scale, standreplacing crown fires
• Auto-successional (fire climax)
ecosystem
• Pinus clausa (sand pine) is
serotinous
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Given this knowledge of fire
ecology:
Sand pine doesn’t burn well
unless it’s a drought, or around
March-May when resin content
is highest and MC is lowest
The cones require high heat;
the crowns of the trees must be
burned
The seeds require bare mineral
soil
Younger trees don’t produce
enough viable seeds to
regenerate a stand, are killed
by fire
Importance of fire severity: P. clausa
seedling recruitment
Senescent
a
Mature
adequate for
overstory restocking
a
a
a
b b
b b
Low density, mature overstory
(BA < 15 m2/ha)
 Small regeneration gaps
 Grassy understory, diverse
herbaceous component
 High C sequestration
 Low hardwood occupancy
 Wildlife habitat function
(imperiled species: red
cockaded woodpecker, gopher
tortoise, skink, etc.)
 Wildfire mitigation function:
reduce severity by reducing fuel
loads



Directly
 Fire Frequency
 Fire Season
 Area Burned
Indirectly
 Fire Type
 Fire Intensity
 Fire Severity
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Southern Fire Exchange: hub for resources
http://southernfireexchange.org/index.html
Competition for moisture, nutrients & light are
temporarily reduced
 Species composition and successional stages are
altered

 Earlier seral stage, but not always

Structure of community may change
 e.g. susceptibility to blowdown
 Fuel profiles may change fire effects

Certain species may be selectively eliminated or
selected for based on their degree of fire adaptation
 This changes over the life cycle of a plant/ phenology
Flower & seed production
stimulated (e.g. wiregrass)
 Seed germination stimulated
(seed or soil conditions)
 Rapid growth & development (e.g.
longleaf pine)
 Fire-resistant bark, self pruning of
ladder fuels (most pines, mature
hardwoods)
 Adventitious buds (gallberry, pond
pine)
 Root/ tuber/ rhizome sprouting,
and storing carbohydrates (oaks,
saw palmetto, perennial grasses)
 Serotinous cones (sand pine)
 Flammability (?)

0
15
2
14
4
13
6
12
10
8
6
4
2
0
12
Time (min)
Foliage mortality
Temperature F
Hiers et al. Final Report: JFSP 01-1-3-11

Crown scorch (dead foliage)
 increases as air temperature
increases
 may not kill crowns of longleaf
and slash pines

Crown mortality affected by:
 stand & shrub density
 fuel concentrations at the base of
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
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
trees
bud dormancy & heat resistance
foliar moisture content
presence of flammable compounds
Season!!! Resistance high when
dormant, lower in late summer
Stem & cambium mortality
affected by:
 bark thickness & heat resistance
 stem diameter & degree of heat
girdling
 heat received during all stages
of combustion
 Damage to tree stems managed
by:
 controlling fire intensity, flame
length, and residence time
 reducing duff & litter
consumption where long
unburned

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Root mortality affected by:
 depth of lateral and feeding
roots
 moisture content of
duff/litter and surface soils
 duration of fire heating

Damage to roots managed
by:
 knowing where roots are
located
 regulating duff & litter
consumption by burning at
specified moisture contents
 Drought indices are
important to consider
 Influence duff consumption
Hiers et al. Final Report: JFSP 01-1-3-11

Fuel & stand characteristics affect lethal heating

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Heat disperses in open stands
High fuel loads increase heat release
High fuel moisture content decreases heat
Litter and duff accumulations increase heating at
base of stem
Therefore, burn prescriptions also affect
mortality: fire regime attributes:
 Frequency: Frequent fires reduce fuel loads
 Intensity: Ignition pattern (how so?)
 Season of burn

Mortality may develop
slowly (even over a
period of several years)
 Damage in one part of
plant stresses other
parts
 Secondary infection by
insects or fungi
 Post burn environment
matters (drought/rain)
Bark beetle
pitch tubes

Sprouting is the recovery mechanism in most
hardwoods and shrubs:
Roots, root crowns, dormant stem buds, rhizomes
Survival related to depth, location
dependent on season and fire severity
 most sprouting: low intensity, dormant season burns
 least sprouting:
▪ high intensity, growing season fires
▪ low soil moisture
▪ High organic matter consumption
 exceptions when reproductive parts deep in soil

Reproduction by seed after a prescribed fire
can be managed by:
 knowing the seed ecology of a species
 Burn prescription
 size and/or intensity of burn- seeding species often
require bare mineral soil. What does this suggest about
desire litter/duff consumption/ severity?
 season/timing of burn- post burn precipitation is
important!

Schedule burns to take advantage of
seasonal responses
 Plants vary in adaptations to fire
 Fire effect is created by interaction of weather,
fuel conditions, fire behavior, & site moisture
 Post-fire conditions significantly affect
recovery & productivity
 Plant community responses are predictable, if
you learn about plant ecology
 Landowner should monitor burning conditions
and post-fire responses and make changes to
subsequent prescriptions as necessary
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Many Florida species have
evolved in a fire environment
Mortality levels are generally low
(direct effects)
Indirect effects on cover and
food sources can be substantial
but vary across the landscape
and diminish with time
Smokey’s
great
grandson?
• Animals with
limited mobility
(young, old, small
animals) are more
vulnerable to injury
and mortality than
animals with high
mobility (mature or
larger animals, flying
species).
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Cover is temporarily decreased
Microclimate is modified
Food sources & nutritional quality increase
 plant species diversity increases
 foliage of new herbaceous plants and shrub
sprouts is more palatable and higher in nutrients
(N,P) and crude protein
 seed production of many species increases
 abundance and diversity of insects may increase
 prey are more visible for predators
For Wildlife in General, Create
Habitat Diversity
Grant Steelman
Example: WILD TURKEY ROTATION PATTERN
Mixed burn rotations such as the one above with a
three year rotation provide adequate nesting and
escape habitat when the adjacent unit has been
burned. Mix dormant/growing season burns (Grant
Slide: Grant Steelman
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Increase number of stems of many
hardwoods and shrubs ***
Generally doesn’t kill larger diameter
hardwoods (e.g. oaks)
Favors bird species that prefer shrubby hardwood habitats
May Burn
August Burn
FIRE SEASON: EFFECTS ON UNDERSTORY, FIRE
BEHAVIOR, SUMMER VS. WINTER
Saw palmetto: 80% annual growth in summer
10 mo. post burn

Deciduous hardwoods most susceptible to
damage
 Can be top killed after leafing out, don’t have carbo.
Reserves to respond
 Positive for hardwood control
 May be a negative for mast production for wildlife

May damage gamebird nests and brood, but
food supplies probably not a problem,
especially with patchy fires

Stimulate flowering/seed production
of many grasses and forbs
 increase number of original plants that flower
 increase number of flowering stems per original
plant

Higher damage to shrubs and
hardwoods
 Top-kills larger, more stems than
dormant season burn
 reduces amount of resprouting
 increases percentage of individuals
completely killed

If fire conducted during rainy, humid
weather, results may be more patchy than
in dry weather
 a positive for wildlife habitat
 a negative for some other objectives


Small pines may be damaged by intense
fire if ambient temperatures are high
Favor birds that prefer open woodlands &
grasslands
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Evergreen trees (pines) & shrubs (including
palmetto & gallberry) most susceptible to
damage!!!!
Most hardwoods will not be affected
How do we manipulate fire to achieve desired
ecological effects? Burn Prescription
Parameters.
What will influence fire’s behavior that will result in
specific ecological effects?
Fire in Florida
1) Weather parameters before, during, and after
the burn (Air temp., RH, precipitation, wind)
2) Timing of the burn
3) Ignition patterns
Firing Plans/Ignition Patterns
1) Slow moving fires of all types are hotter at the soil surface,
and have more potential to heat and ignite ground
(subsurface) fuels and affect roots and soil
Fire in Florida
2) To minimize the degree of fire
severity, limit the fire residence
time
3) The pattern of ignition (how the fire
is applied, could be solid line, point
source or a combination) will alter
the intensity of the resultant fire
 ecological effects


Major factors that influence ecosystems:
 Depth to water table
 Fire frequency, fire regimes
Effects on animals include:
 Direct Mortality - MINOR
 Habitat changes – can be MAJOR (+)

Wildlife, plant diversity and numbers
increase with a mosaic of successional
stages created by a variety of fire
prescriptions over time
 Pyrodiversity promotes habitat diversity
promotes species diversity

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